Electron Configurations, Isoelectronic Elements, & Ionization Reactions Chemistry 11

Note: Of the 3 subatomic particles, the electron plays the greatest role in determining the physical and chemical properties of an element. Of the 3 subatomic particles, the electron plays the greatest role in determining the physical and chemical properties of an element. There is a relationship between the electron configuration of elements and their arrangement in the table. There is a relationship between the electron configuration of elements and their arrangement in the table.

Elements are Classified into 4 Categories: Noble Gases are elements in which the outermost s and p sublevels are filled. Noble Gases are elements in which the outermost s and p sublevels are filled. They are also called inert gases because they do not participate in many chemical reactions. They are also called inert gases because they do not participate in many chemical reactions. Argon (Ar) 1s 2 2s 2 2p 6 3s 2 3p 6 Argon (Ar) 1s 2 2s 2 2p 6 3s 2 3p 6 Neon (Ne) 1s 2 2s 2 2p 6 Neon (Ne) 1s 2 2s 2 2p 6

Representative Elements Also known as Main Group Elements Also known as Main Group Elements Are elements whose outermost s or p sublevels are only partially filled. Are elements whose outermost s or p sublevels are only partially filled. Sodium (Na) 1s 2 2s 2 2p 6 3s 1 Sodium (Na) 1s 2 2s 2 2p 6 3s 1 Silicon (Si) 1s 2 2s 2 2p 6 3s 2 3p 2 Silicon (Si) 1s 2 2s 2 2p 6 3s 2 3p 2

Inner Transition Metals The Actinides & Lanthanides The Actinides & Lanthanides Are elements whose outermost s sublevel and the nearby f sublevel generally contain electrons. Are elements whose outermost s sublevel and the nearby f sublevel generally contain electrons. Gadolinium (Gd) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 8 Gadolinium (Gd) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 8

Transition Elements Are elements whose outermost s sublevel and nearby d sublevel contain electrons. Are elements whose outermost s sublevel and nearby d sublevel contain electrons. Iron (Fe) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6 Iron (Fe) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6

Transition Metals Do not form ions with noble gas configurations Do not form ions with noble gas configurations If they did, they would have to lose 4 or more electrons, and the energy needed to do this would be too high. If they did, they would have to lose 4 or more electrons, and the energy needed to do this would be too high. These metals do form cations (“+” charged ion) with more than one charge (multi-valent) These metals do form cations (“+” charged ion) with more than one charge (multi-valent) Electrons are first moved from the outer “ s ” and then inner “ d ” sublevels. Electrons are first moved from the outer “ s ” and then inner “ d ” sublevels.

Example 1: 25 Mn ( 18 Ar)4s 2 3d 5 25 Mn ( 18 Ar)4s 2 3d 5 Mn 2+ loses 2 electrons from the “s” sublevel Mn 2+ loses 2 electrons from the “s” sublevel Mn 2+ ( 18 Ar)4s 0 3d 5 Mn 2+ ( 18 Ar)4s 0 3d 5

Example 2: 26 Fe( 18 Ar)4s 2 3d 6 26 Fe( 18 Ar)4s 2 3d 6 Fe 2+ loses 2 electrons from the “s” sublevel Fe 2+ loses 2 electrons from the “s” sublevel Fe 2+ ( 18 Ar)4s 0 3d 6 Fe 2+ ( 18 Ar)4s 0 3d 6 Fe 3+ ( 18 Ar)4s 0 3d 5 Fe 3+ ( 18 Ar)4s 0 3d 5

Valence Electrons Are the electrons in the highest occupied energy level of an element’s atom. Are the electrons in the highest occupied energy level of an element’s atom. Are usually the only electrons used in the formation of chemical bonds. Are usually the only electrons used in the formation of chemical bonds.

Valence Electrons Note: Many of the similar chemical properties of elements in the same group (vertical column) are related to the  number of “ s ” and “ p ” electrons in the highest occupied energy level. Many of the similar chemical properties of elements in the same group (vertical column) are related to the  number of “ s ” and “ p ” electrons in the highest occupied energy level. These electrons are valence electrons. These electrons are valence electrons.

Example 1: Sodium 11 Na 11 Na 1s 2 2s 2 2p 6 3s 1 1s 2 2s 2 2p 6 3s 1 Highest energy level = 3 Highest energy level = 3 Single “s” electron Single “s” electron No “p” electrons for this element No “p” electrons for this element  Na has 1 valence electron  Na has 1 valence electron

Example 2: Phosphorus 15 P 15 P 1s 2 2s 2 2p 6 3s 2 3p 3 1s 2 2s 2 2p 6 3s 2 3p 3 Highest energy level = 3 Highest energy level = 3 Two “s” electrons Two “s” electrons Three “p” electrons Three “p” electrons  5 valence electrons  5 valence electrons

Example 3: Potassium 19 K 19 K Electron Configurations Electron Configurations 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 Highest energy level = 4 Highest energy level = 4  1 valence electron  1 valence electron

Example 4: Carbon 6 C 6 C Electron Configuration Electron Configuration 1s 2 2s 2 2p 2 1s 2 2s 2 2p 2 Highest energy level = 2 Highest energy level = 2  4 valence electrons  4 valence electrons

Example 5: Magnesium 12 Mg 12 Mg Electron Configuration Electron Configuration 1s 2 2s 2 2p 6 3s 2 1s 2 2s 2 2p 6 3s 2 Highest energy level = 3 Highest energy level = 3  2 valence electrons  2 valence electrons

Example 6: Oxygen 8 O 8 O Electron Configuration Electron Configuration 1s 2 2s 2 2p 4 1s 2 2s 2 2p 4 Highest energy level = 2 Highest energy level = 2  6 valence electrons  6 valence electrons

Answers 1. On the sketch of the Periodic Table, label: a) the periods b) the group numbers c) colour the “s block” elements (red) d) colour the “p block” elements (blue) e) colour the “d block” elements (green) f) colour the “f block” elements (yellow)

Question 2 Read the following electron configurations to determine the identities of the following elements: a) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3 d10 4p 6 5s 2 b) 1s 2 2s 2 2p 6 3s 2 3p 3 c) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 5d 10 6p 6 d) 1s 2 2s 2 2p 2 e) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 5

Question 3 Write ionization reactions for the following elements: a) N is a non-metal, so it will gain electrons. It needs 3 more electrons to become as stable as a Noble Gas, so it will gain three electrons. Show gained electrons on the left-hand side of the arrow.

Question 3 b) Sc is a metal, so it will lose electrons. It needs to lose 3 electrons to become as stable as a Noble Gas. Show lost electrons on the right-hand side of the arrow.

Question 3 c) P is a non-metal, so it will gain electrons. It needs 3 more electrons to become as stable as a Noble Gas, so it will gain three electrons. Show gained electrons on the left-hand side of the arrow.

Question 3 d) Rb is a metal, so it will lose electrons. It needs to lose 1 electron to become as stable as a Noble Gas. Show the lost electron on the right-hand side of the arrow.

Question 3 e) Se is a non-metal, so it will gain electrons. It needs 2 more electrons to become as stable as a Noble Gas, so it will gain two electrons. Show gained electrons on the left-hand side of the arrow.

Question 4 Explain what is meant by the term “ isoelectronic ”. Answer : The prefix “ iso ” means “the same ”, so isoelectronic means that two atoms or ions have the same number of electrons or the same electron configuration.

Question 5 What are four ions, with their charges, that are isoelectronic with each of the following: a) neon : N 3– O 2– F 1– Na 1+ Mg 2+ Al 3+ b) argon : P 3– S 2– Cl 1– K 1+ Ca 2+ Sc 3+ c) krypton : As 3– Se 2– Br 1– Rb 1+ Sr 2+ Y 3+ d) an S 2– ion : P 3– Cl 1– K 1+ Ca 2+ Sc 3+

Question 6 A calcium ion, Ca2+, is isoelectronic with argon.Does this mean that calcium has turned into argon? Explain. Answer : No, calcium has not turned into Argon. Remember, it is the atomic number (number of protons) that determines what type of element an atom is. The calcium ion has the same number of electrons as an Argon atom. This just means that they are Both stable octet with 18 electrons.

Question 7 Write the electron configuration for the element with atomic number 117. In which chemical group does it belong? Predict the charge on the ion that it will form.

Question 7 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 6 7s 2 5f 14 6d 10 7p 5 This element belongs to the Halogen family or Group 17 (VIIB). It will gain one electron to have the same configuration as a Noble Gas, so it will form ions with a charge of 1-.